Editor's note: Julian E. Zelizer is a professor of history and public affairs at Princeton University's Woodrow Wilson School. His new book, "Arsenal of Democracy: The Politics of National Security -- From World War II to the War on Terrorism," will be published this fall by Basic Books. Zelizer writes widely about current events.

Julian E. Zelizer says there's no guarantee that President Obama will achieve national health care reform.

(CNN) -- All the stars seem to have aligned for the passage of national health care reform. Victory, supporters say, is inevitable.

During the past week, two important developments excited health care proponents.

First, President Obama and Senate Democrats included reconciliation instructions in the budget for health care. If a deal is not reached by October, congressional Democrats can use a process that prohibits a filibuster and allows passage of the bill with 51 rather than 60 votes in the Senate.

And even if opponents of the bill attempted to stage a filibuster, the switch of Sen. Arlen Specter to the Democratic Party, combined with the likely victory of Al Franken as a senator from Minnesota, would provide Democrats with 60 votes to fight it off.

Yet, as the Grateful Dead sang in one of their most famous songs, "When life looks like Easy Street, there is danger at your door."

In 1993, President Clinton also had reason to believe that the passage of health care reform was going to happen.

More than 35 million people did not have coverage, and the costs of health care were skyrocketing. Polls showed strong support for comprehensive reform. Business, labor, progressive activists and legislators in both parties were prepared to reach an agreement. Key members of the health care community, including the American Medical Association, were open to reform.

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The president was determined to make this a defining achievement for his administration.

"If I don't get health care, I'll wish I didn't run for president," he said.

There were 57 Democrats in the Senate and a strong Democratic majority in the House (with more moderate Republicans than exist today).

Yet things went terribly wrong. About a year after Clinton made his proposal, the legislation was dead, and Republicans used the bill as the basis of their "Contract with America" to retake control of the House and Senate.

Clinton faced several problems that Democrats might want to consider in the next few months.

The first had to do with the complexity of the legislation.

Clinton tried to find a middle ground that would attract moderate Democrats without angering liberal House Democrats who wanted a single-payer insurance system. A health care task force, headed by Hillary Clinton, brought together health policy experts to craft a plan.

The final proposal created an employer mandate requiring that businesses provide coverage to at least 80 percent of their workers. Large employers would buy their health plans from regional alliances that would theoretically lower the cost of premiums through competition. Federal regulations would limit how high premiums could rise. Finally, the government would provide coverage for the poor and unemployed, using savings from Medicare, Medicaid and tobacco taxes.

The proposal might have been sound policy, but it didn't work politically. Republicans attacked this as an example of big-government liberalism. The complexity of the proposal offered the GOP an opportunity to launch these kinds of attacks even though the program itself was as far from "socialized medicine" as one could imagine.

A trade association representing small businesses opposed the employer mandate as a tax. Health insurers, fearing that they could be squeezed out under the new system, broadcast a devastating television commercial that featured a suburban couple, Harry and Louise, expressing their confusion about the plan and their worry that the government would make health care decisions.

Because Congress had not been brought into the task force discussions, many legislators were more willing to criticize the president.

The second problem was timing. As the health care task force worked on the plan, Clinton allowed the administration to get distracted by other issues, namely a highly partisan federal budget battle. The delay in sending a bill to Congress allowed opponents to gather momentum and put together their attack. During the summer, Democrats were pressured to vote on a budget that increased taxes in order to reduce the deficit.

This led to a third and more difficult problem, the question of who should pay for the health care program.

This issue divided Democrats as much as it created partisan tension. Republicans branded the employee mandate as a tax, and moderate Democrats, led by Tennessee Sen. Jim Cooper, proposed a much more limited alternative that did not include an employer mandate. The administration tried to negotiate a compromise with the centrist coalition but failed to reach an agreement.

In general, political conditions are better for Democrats today than they were at the beginning of Clinton's term. Obama's victory was much stronger than was Clinton's in 1992, which got only 43.6 percent of the vote. Americans are more familiar with the managed-care health system and the structural changes that were just starting to take place when Clinton was in the White House.

More important, Democrats now have the experience of 1993, which will make them more cautious about avoiding the same mistakes. For example, unlike Clinton, Obama has been very careful to remain vague about what kind of legislation he wants and to give Congress considerable room to work on the details of the bill

But some of the older pitfalls remain. The administration and congressional Democrats need to reach an agreement sooner rather than later about how these benefits will be financed, or they will be bogged down by the same kinds of internal conflicts over taxes. Once they have a plan in place, Democrats also need to think of an effective way to package it to the public in order to counteract attacks from Republicans who may characterize it as socialized medicine.

If Democrats are able to achieve national health care reform, they will go into the 2010 and 2012 election with a major, concrete political achievement. If they fail, as Clinton's experience reminds us, they might give Republicans the kind of issue that they have been looking for to recover from 2008.

The opinions expressed in this commentary are solely those of Julian E. Zelizer.